Engineering and construction group Monadelphous has announced $320 million in new contracts for Rio Tinto in the Pilbara.

Monadelphous said it had received a notice of award for structural, mechanical and piping works at Rio's Marandoo mine phase 2 expansion project, located around 45 kilometres east of Tom Price.

Also today, Monadelphous said it had been awarded three-year extensions to two shutdown and maintenance service contracts for Rio's coastal and inland west operations.

The contracts were awarded under a framework agreement Monadelphous and Rio first announced in Feburary.

"We are pleased to continue our extensive support for Rio Tinto in the Pilbara through the ongoing maintenance work and our first contract under the framework agreements," managing director Rob Velletri said.

At 10:20AM, WST, Monadelphous shares were down 1.3 per cent, trading at $20.74.